Stuffing Box Venting

[sow]

Hello,

Generally when a dry well vertical centrifugal pump (e.g. an immersible Flygt type sewage pump or a long shaft driven centrifugal) is installed it is common practice to install a air vent in or around the stuffing box area. I understand that this is to do with removing air away from the mechanical seals.

However this is impractical to do on submersible pumps, and to my knowledge is never done.

A few things that spring to mind are:

1) Is the air vent unnecessary on dry well vertical pumps?

2) If it is necessary on dry well pumps then why is it not needed on submersible pumps?

3) What special features do I need to look for in a submersible pump in order to prevent air build up or adverse effects of air build up around a mechanical seals?


Thanks

 

[PumpSmart]

Sow,
Immersible and submersible pumps are different.
Immersible are partial submerged and submersible total
(pump+motor)submerged.
1. Not always. Depends on pump design.
If pump is selfventing design, it does not need it.
2. Inmmersible and Submersible pumps does not have mechanical seals and Submersible pump is selfventing.
Motors provided in Immersible pumps have a Double seal
as standard.
Immersible pump is not selfventing.
3. Just to be selfventing.

 

[sow]

Thanks - I think we have different interpretations of the terminology used for pumps and seals - however that aside what would make a pump self venting?

 

[Artisi]

It all comes down to pump design - some need to have vented seal areas and some don't. There is no fixed rule on needed or not needed. The easiest way to decide if it needs to be self-veting is to ask the manufacturer.

 

[josephf]

Hello,
I noticed an old thread that sow had posted regarding hydropower in a sewage works project. Did anything ever come of that project?
Thanks,
Joe...

 

[sow]

We are currently installing a reverse Archimedes screw downstream of the inlet works. (200kW) I think these may even be suitable for installation on raw sewage. Its basically an Archimedes pump with a generator rather than a motor.

We could only find a couple of other hydro installations on sewage - and these were on treated final effluent, cleaner than most rivers in terms of gross solids. Generally low - medium head systems such as Kaplans / bulbs were used. Need to think twice about using these on screened sewage, although some rivers must have more gross solids than screened sewage! (however bear in mind all screenings are not removed by inlet works). Raw sewage probably out of the question for more traditional hydro.

Glad to give any more info required.